An improved technology for electronic component monitoring devices that rely on characteristics of electronic components with bumps has already been proposed in Japanese Laid-open patent H8-153997.
Such an electronic component monitoring device is explained with reference to FIGS. 6, 7A, and 7B.
In FIG. 6, an electronic component with bumps 1 has a molded main body 2, and a substrate 3 provided underneath the main body 2. A plurality of bumps 4 are formed in a matrix pattern on the bottom face of the substrate 3 as terminals of the electronic component with bumps 1. The bumps 4 have a semi-spherical shape and mirror-like and curved surface. Bumps 4 are preferably comprised of solder, gold or any other conductive or semicondutive material suitable as terminals.
The electronic component with bumps 1 is held by a nozzle 5 disposed at the lower part of a transfer head 6 by suction force. A background board 7 is attached to the transfer head 6 behind the electronic component with bumps 1.
A light source unit 8 having a concave area 9 on its upper part is provided below the electronic component with bumps 1. A lens-barrel 10 which runs through the center of the light source unit is provided at the lower part of the concave area 9. A camera 11 attached to the lens-barrel 10 monitors the bottom face of the electronic component with bumps 1 through the lens-barrel 10 and concave area 9.
Numerous LEDs 12, which emit light toward the bottom face (bumps 4) of the electronic component with bumps 1, are disposed on angled planes of the concave area 9. An optical fiber 14 connected to a halogen light source 13 is provided at both sides of the light source unit 8 to light-up the background board 7 from the direction of arrow marks N1 and N2 shown in FIG. 6.
As shown in FIG. 7A, bump 4 is secured on a land 15 formed on the bottom face of the substrate 3. However, in some instances a bump 4 is missing and the land 15 is exposed at the bottom face of the substrate 3, as shown by A in FIG. 7A. Such an electronic component with bumps 1 is defective, and may need to be rejected from the line.
With the electronic component monitoring device of the prior art as configured above, the land 15, which is made of a metal foil such as copper and has an even metal surface, brightly shines as a result of the emitted light.
FIG. 7B shows an image monitored by the electronic component monitoring device of the prior art as shown in FIG. 6. In FIG. 7B, shaded portions indicate bright areas, and other portions indicate dark areas. A point P1 indicates a corner 3a of the substrate 3, and images S1 and S2 are the part A in FIG. 7A.
It is apparent that there is no difference between the image S2, which corresponds to the land 15 only, and the image S1, which corresponds to a land 15 and bump 4 combination.
An image processing unit of the prior art thus erroneously judges this part which, in fact, should be designated "defective." Accordingly, the electronic component monitoring device of the prior art has low reliability in recognizing the electronic component with bumps 1. As a result, an electronic component may be mounted on a substrate at an erroneous bump position due to erroneous recognition of a wiring pattern near the land 15.